JP4532821B2 - Apparatus and method for detecting arterial blood flow problems during extracorporeal blood processing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, for example, uses a blood pump to pump blood from a blood access site through an arterial cannula and an arterial blood line into the blood processing device and from the blood processing device through a venous blood line and a venous cannula. The present invention relates to a method for detecting arterial blood flow problems during extracorporeal blood processing such as dialysis therapy returned to a patient. The invention further relates to a blood treatment device, such as a dialysis device, for carrying out this method.
[0002]
[Prior art]
In order to monitor arterial blood flow problems, well-known dialyzer measures the pressure in the extracorporeal arterial blood line. If a problem occurs at the blood access site, such as due to cannula aspiration at the inner wall of the blood access site, the arterial pressure drops below a defined threshold. The dialyzer then stops the blood pump to prevent damage to the blood access site. In addition, the venous clamp is closed, and further alarm sounds and alarm lamps are triggered.
[0003]
Another function of arterial pressure measurement is to monitor the connection between the cannula and the blood access site. When the connection between the patient and the machine is broken at the arterial joint, the machine-side protection system based on pressure reacts within seconds.
[0004]
In a well-known dialysis machine, a pressure sensor is generally used for both an arterial blood line and a venous blood line. Further, in the dialysate system, a pressure sensor is generally prepared. For this reason, a protection system based on arterial pressure measurement can be introduced into well-known dialysis machines without the need for significant costs.
[0005]
The well-known hemodialyzer arterial pressure sensor is connected to the arterial blood line through a pressure line. The disadvantage here is that blood and air contact in the pressure line as a result of the arterial pressure measurement. In addition, if the pressure line and the pressure sensor are not properly connected, there is a risk of air entering the extracorporeal circulation.
[0006]
The dialyzer can be simplified in configuration by abandoning the arterial pressure measurement. However, as a result, monitoring at the blood access site according to well-known methods is no longer possible.
[0007]
German Patent Application No. A-19901078 describes a method for early detection of stenosis during extracorporeal blood processing. In order to detect stenosis, it has been proposed to monitor the width of pressure fluctuations in the extracorporeal circulation derived from the pulse (see, for example, Patent Document 1).
International Patent Application No. 97/10013 describes a blood processing device that allows detection of the location of a needle within a patient's fistula. This device uses a single arteriovenous pressure sensor located in the blood delivery and drainage line. In the first embodiment, pressure fluctuations in the blood line caused by heartbeat are evaluated, but fluctuations caused by the blood pump are excluded. In another embodiment, an assessment of pressure fluctuations due to blood pumps in the arterial blood line is certainly scheduled, but if pressure fluctuations are no longer detected, access to the fistula (瘻) is inaccurate. It is inferred that there will be (see, for example, Patent Document 2).
[0008]
[Patent Document 1]
German Patent Application Publication No. 19901078 [Patent Document 2]
International Publication No. 97/10013 Pamphlet [0009]
[Problems to be solved by the invention]
It is an object of the present invention to provide a method for detecting arterial blood flow problems during extracorporeal blood processing without using arterial pressure measurement. Another object of the present invention is to produce a blood processing apparatus that can detect arterial blood flow problems without using arterial pressure measurement.
[0010]
[Means for Solving the Problems]
These problems are solved with the features of claims 1 and 2 or 6 and 7.
Arterial blood flow problems are blood line damage upstream of the blood pump in extracorporeal circulation. In particular, the invention relates to the detection of obstructions such as those caused by aspiration of an arterial cannula or bending of a tubular blood line.
[0011]
In the method according to the invention, arterial blood flow problems are detected based on pressure measurements on the venous side and / or dialysate side. From the analysis of the pressure signal width variation, arterial blood flow problems such as arterial cannula aspiration or arterial blood line bends are inferred.
[0012]
In experimental investigations, when the blood flow deteriorates upstream of such a blood pump, the range of periodic fluctuations in the pressure in the venous blood line can be significantly increased due to the peristaltic blood pump in the arterial blood line. Proven. When a tube type roller pump is used, the venous pulse pressure generated by the rotation of the motor is inversely proportional to the filling of the pump tube section. On the other hand, the filling of the pump tube section depends on the arterial pressure in the extracorporeal circulation. When arterial pressure is low, the pump tube section collapses partially, thereby reducing the effective blood flow carried.
[0013]
The increase in pulse pressure width upstream of the blood pump occurs as a result of partial collapse of the pump tube section when the arterial pressure is low. The hose section partially collapsed due to the negative pressure is rapidly filled at the moment when the closed roller pump is opened. This suddenly reduces the venous pressure upstream of the blood pump and increases the width of the pulse pressure.
[0014]
Since no arterial pressure sensor is required with the pressure line, both blood treatment devices and hose systems can be manufactured particularly cost-effectively. Furthermore, there is an advantage that handling when the blood processing apparatus is expanded or contracted becomes easy. There is no contact between blood and air as a result of arterial pressure measurement. Furthermore, there is no risk of air entering the extracorporeal circulation due to an incomplete connection between the arterial pressure sensor and the pressure line. Since the venous pressure measurement in the well-known dialysis machines is already technically realized, all that is required is to implement an additional evaluation algorithm and change the machine control. Air intrusion due to the disconnection between the patient and the machine can in this case be recognized by an air detector in the existing venous blood line anyway. Even when equipped with an arterial pressure sensor, the present invention can be beneficially used to increase safety during extracorporeal blood processing.
[0015]
The blood processing apparatus is an apparatus that receives a certain effect on blood, such as a hemodialyzer, a blood filter, a hemodialysis filter, a plasma filter, or a blood adsorber. In a dialyzer that uses a dialyzer as a blood treatment device that is separated into a blood chamber and a dialysate chamber by a single semipermeable membrane, pressure fluctuations are all in fluid communication with the dialyzer through the membrane and dialysate chamber. In order to propagate to this part, periodic fluctuations in pressure can be measured not only in the venous blood line but also in the dialysate system.
[0016]
In order to reduce the interference disturbance that occurs with a single width variation, the pulse pressure width is preferably ascertained at long consecutive times within a defined time frame and compared to a threshold value each time. If the width at all successive time points exceeds the threshold, it is inferred that an arterial blood flow problem has occurred.
[0017]
The length of the time frame is preferably at least as large as the reciprocal of the rotational frequency of the blood pump. Thereby, at least one absolute maximum pressure value or minimum pressure value per hour frame is obtained.
[0018]
For example, detection of an arterial cannula aspiration can trigger an alarm and / or an intervention in extracorporeal blood processing, such as closing a venous clamp, for example.
[0019]
The blood treatment device preferably has a calculation device for measuring the width of the periodic pressure fluctuations, and when the width of the pressure fluctuations is compared with a prescribed threshold value and exceeds a threshold value, for example to trigger an alarm or blood treatment And an evaluation device that generates a control signal that can initiate intervention in
[0020]
DETAILED DESCRIPTION OF THE INVENTION
In the following, two embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows the dialysis machine in a simple schematic view. This dialyzer has a dialyzer 1 separated by a semipermeable membrane 2 into a blood chamber 3 and a dialysate chamber 4. An arterial blood line 5 is connected to the inflow port of the blood chamber 3, and a closed blood pump 6 such as a roller pump is connected thereto. The first section 7 a of the venous blood line 7 leads from the outlet of the blood chamber 3 to the inlet of the drip chamber 8. A second section 7 b of the venous blood line 7 is connected to the outlet of the drip chamber 8. Connected to the ends of the arterial blood and venous blood lines 5 and 7 are arteries or venous cannulas 9 and 10 which are pierced into an artery or vein portion of a patient's fistula (not shown).
[0021]
In order to measure the pressure in the venous blood line 7, the dialysis machine is equipped with a measuring device 11. The measuring device 11 may be a pressure sensor prepared in the first section 7a of the arterial blood line. In the second section 7b of the arterial blood line 7, an electromagnetically operated venous hose clamp 12 is connected.
[0022]
The dialysis machine further includes a calculation device 13, an evaluation device 14 and an alarm device 15. The calculation device 13 is connected to the measurement device 11 through a first data line 16, the evaluation device 14 is connected to the calculation device 13 through a second data line 17, and the alarm device 15 is connected to the evaluation device 14 through a third data line 18. Has been. A control line 19 connects the alarm device 15 with the electromagnetically activated hose clamp 12.
[0023]
The computing device 13 exchanges data with the storage device 28 through a data line 27. The computing device, the evaluation device, the storage device and the alarm device may be components of a microcomputer that are present in any well-known dialysis machine.
[0024]
In FIG. 1, the extracorporeal blood circulation of the dialyzer is designated by reference numeral 25 and the dialysate system is designated by reference numeral 26. Extracorporeal blood circulation and dialysate circulation are created from several components as shown in the examples below. It is well known to those skilled in the art that there are numerous embodiments for configuring this device.
[0025]
The dialysate source 20 is prepared with fresh dialysate. A dialysate inflow line 21 leads from the dialysate source 20 to the inlet of the dialysate chamber 4 of the dialyzer 1, while a dialysate outflow line 22 leads from the outlet of the dialysate chamber to the drain 23. The dialysate pump 24 is connected to the dialysate outflow line 22 upstream of the dialyzer 1.
[0026]
In the following, a method for detecting aspiration of an arterial cannula 9 in which the dialyzer is activated by arterial cannula aspiration will be described in detail.
During the extracorporeal blood treatment, the pressure in the venous blood line 7 is measured using the measuring device 11.
[0027]
FIG. 2 shows a temporal transition of the venous pressure P / hPa (mbar) before and after the suction of the cannula. The width ΔP of the periodic pressure fluctuation due to the operation of the blood pump 6 increases by approximately 35% after aspiration and decreases by approximately the same value after the cannula is opened again.
[0028]
The premise of recognizing that the blood access site is not functioning correctly is that the difference from the maximum and minimum pressure values ΔP measured in one time frame S over N consecutive time frames exceeds the threshold M. The condition is to be met:
[0029]
ΔP (S) = P maximum value (S) −P minimum value (S)> M (Equation 1)
[0030]
By evaluating N consecutive data records, the interference interference of the protection system that occurs with a single width variation is reduced. It is the threshold value M that characterizes the sensitivity of the protection system. In general, the following applies. The greater the value of M, the higher the threshold at which a machine alarm is triggered. The following relationship applies:
[0031]
M = ΔP · (1 + x / 100) (Equation 2)
[0032]
Here, parameter x indicates what percentage of ΔP must increase before the machine alarm is triggered. The time frame S for calculating ΔP is the magnitude of the reciprocal of the rotation frequency f of the blood pump.
[0033]
S = 1 / f (Equation 3)
[0034]
This ensures that at least one absolute maximum pressure value or minimum pressure value is known per hour frame. The response time τ of the protection system is given by:
[0035]
τ = N · S (Equation 4)
[0036]
Let's assume that the rotation frequency of the blood pump is about 0.8 s- ¹ . This results in the time frame S of about 1.25 s required for the evaluation of the maximum or minimum pressure value according to Equation 3. During 1.25 s, ΔP (S) is approximately 66 hPa (mbar) before cannula inhalation (FIG. 2). Choosing N = 2 and x = 20% to reduce interference interference, ie, ΔP (S) can be increased by up to 20% for two consecutive values. Equation 2 yields a value of 79.2 hPa (mbar) for M (FIG. 2). After cannula aspiration, ΔP rises by about 92 hPa (mbar). As a result, the protection system triggers a mechanical alarm after τ = 2.5s.
[0037]
First, the numerical values N, S and x that must be used for the evaluation are determined. These numerical values can be stored in the storage device 28, but can also be set by the user. The time frame S can be calculated by the calculation device according to Equation 3 from the rotational frequency of the blood pump 6 set in the dialysis device by the control device or the user.
[0038]
During the extracorporeal blood treatment, the calculation device 13 calculates the width ΔP of the periodic pressure fluctuation in the time frame S at N consecutive time points. These numerical values are stored in the storage device 28. The calculation device 13 calculates the threshold value M according to Equation 2. The evaluation device 14 examines whether ΔP exceeds the threshold value M with respect to the measurement values that are N times consecutive. When the threshold value M is exceeded, the evaluation device 14 provides a control signal to the alarm device 15. The alarm device 15 then triggers an alarm sound and / or alarm lamp, and the electromagnetically actuated valve 12 closes the venous blood line.
[0039]
FIG. 3 shows another embodiment of the dialysis machine. The dialysis device according to FIG. 3 differs from the device according to FIG. 1 only in that the measuring device 11 ′ measures the pressure in the dialysate system 26, not in the venous pressure line. The measuring device 11 ′ may be a pressure sensor prepared in the dialysate transport line 22, for example. Corresponding parts of the dialysis device according to FIGS. 1 and 3 are given the same reference numerals.
[0040]
FIG. 4 shows the time transition of the pressure on the dialysate side before and after cannula suction. The pressure range on the dialysate side also increases after cannula suction. Therefore, the analysis of the pressure signal is carried out in the dialysis device according to FIG. 3 in the same way as the device according to FIG.
[Brief description of the drawings]
FIG. 1 is a simplified schematic diagram of one embodiment of a dialysis machine.
FIG. 2 is a relationship diagram showing venous pressure as a function of time before and after aspiration of an arterial cannula at the inner wall of the blood access site.
FIG. 3 is a simplified schematic diagram of a second embodiment of a dialysis machine.
FIG. 4 is a relationship diagram showing dialysis pressure as a function of time before and after arterial cannula aspiration.

Claims (3)

An arterial cannula (9) connected to the blood pump (6) through the arterial blood line (5) and connected to the inlet of the blood processor (1);
A venous cannula (10) connected to the outlet of the blood processor through a venous blood line (7);
A measuring device (11) for measuring the pressure in the venous blood line;
A blood processing apparatus comprising a calculation device (13) for determining a width (ΔP) of periodic pressure fluctuations in a venous blood line,
The calculation device (13) determines the pressure fluctuation width (ΔP) caused by the blood pump in the arterial blood line, and compares the pressure fluctuation width caused by the blood pump with the threshold value (M). A blood processing apparatus comprising: an evaluation device (14) that detects an arterial blood flow problem and generates a control signal when the blood pressure exceeds. Blood chamber (3) of dialyzer (1) connected to blood pump (6) through arterial blood line (5) and separated into blood chamber and dialysate chamber (4) by one semipermeable membrane (2) An arterial cannula (9) connected to the inlet of
A venous cannula (10) connected to the outlet of the blood chamber through a venous blood line (5), the dialysate chamber being part of the dialysate system (26);
A measuring device (11 ′) for measuring the pressure in the dialysate system;
A dialysis machine comprising a calculation device (13) for determining a width ΔP of periodic pressure fluctuations in the dialysate system,
The calculation device (13) determines the pressure fluctuation width (ΔP) caused by the blood pump in the arterial blood line, and compares the pressure fluctuation width caused by the blood pump with the threshold value (M). And an evaluation device (14) for detecting an arterial blood flow problem and generating a control signal when the blood pressure exceeds the range. When the N times successive time frame (S) in the width ([Delta] P) exceeds the threshold (M), the evaluation device (14) according to claim 1 or 2, wherein the generating a control signal Blood processing device.

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